1. Field of the Invention
The present invention relates to techniques for managing keys that are used to encrypt and decrypt data. More specifically, the present invention relates to a method and an apparatus for maintaining keys in a limited amount of space (for example, on a memory-constrained computing device such as a smart card) using auxiliary, less-trusted storage, that can be copied for robustness, in such a way that keys can be deleted, and once deleted, cannot be recovered, even if the copies on auxiliary storage are still available.
2. Related Art
In order to protect sensitive data from unauthorized access, organizations commonly store sensitive data in encrypted form. If the encrypted data needs to be accessed, is must first be decrypted using a decryption key. However, such decryption keys can, over time, be obtained by an adversary through compromise or coercion. To remedy this problem, keys can be stored in tamper-resistant smart cards, in which case it is not feasible to covertly discover the keys.
Unfortunately, smart cards have limited storage space. This is a problem because decryption keys are often private keys (from a private/public key pair) which tend to be quite large. Hence, the limited storage space on a smart card makes it impractical (if not impossible) to store a large number of private keys on the smart card. This restriction significantly limits the capabilities of a system that uses a smart card to manage keys.
Hence, what is needed is a method and an apparatus that can maintain a large number of keys while providing the protection of a smart card.